Wafer level package utilizing molded interposer

ABSTRACT

A molded interposer includes a layer of first molding compound having a first side and a second side opposite to the first side; a first redistribution layer (RDL) structure disposed on the first side; a second redistribution layer (RDL) structure disposed on the second side; a plurality of metal vias embedded in the layer of first molding compound for electrically connecting the first RDL structure with the second RDL structure; and a passive device embedded in the layer of first molding compound.

TECHNICAL FIELD

The present disclosure relates generally to the field of semiconductorpackaging. More particularly, the present disclosure relates to a waferlevel package (WLP) utilizing a molded interposer with integratedpassive devices (IPDs) embedded in the molded interposer.

BACKGROUND

2.5D semiconductor package such as CoWoS (Chip-on-Wafer-on-Substrate) isknown in the art. CoWoS (Chip-on-Wafer-on-Substrate) typically usesThrough Silicon Via (TSV) technology to integrate multiple chips into asingle device.

This architecture provides higher density interconnects, decreasesglobal interconnect length, and lightens associated RC loading,resulting in enhanced performance and reduced power consumption on asmaller form factor.

Conventionally, the TSV silicon interposer is costly because fabricatingthe interposer substrate with TSVs is a complex process. Thus, formingWLP products that include a TSV interposer may be undesirable forcertain applications.

Further, 2.5D semiconductor package places several dies side-by-side ona TSV silicon interposer. Passive devices such as capacitors orresistors may be mounted on the same surface on which the dies areplaced. This arrangement results in a TSV interposer with a largersurface area. It is usually desirable to shrink the size of theinterposer.

BRIEF SUMMARY

The present disclosure is directed to provide an improved moldedinterposer with a smaller size, and a semiconductor package using thesame.

In one aspect of the disclosure, a molded interposer includes a layer offirst molding compound having a first side and a second side opposite tothe first side; a first redistribution layer (RDL) structure disposed onthe first side; a second redistribution layer (RDL) structure disposedon the second side; a plurality of metal vias embedded in the layer offirst molding compound for electrically connecting the first RDLstructure with the second RDL structure; and a passive device embeddedin the layer of first molding compound. The passive device iselectrically connected to the first RDL structure through a plurality ofconnecting elements.

In another aspect of the disclosure, a semiconductor package includes amolded interposer as described above; and at least one semiconductor diemounted on the first RDL structure. The semiconductor die isencapsulated by a second molding compound. The first molding compoundand the second molding compound have different compositions.

In still another aspect of the disclosure, a method for fabricating asemiconductor package is disclosed. A first carrier is provided. A firstredistribution layer (RDL) structure is formed on the first carrier. Atemplate layer is formed on the first RDL structure. Via openings areformed in the template layer. Metal vias are formed in the via openings.The template layer is then removed. A passive device is mounted on thefirst RDL structure. The passive device and the metal vias are moldedwith a layer of first molding compound. The layer of first moldingcompound is subjected to a grinding process to expose end surfaces ofthe metal vias. A second redistribution layer (RDL) structure is formedon the layer of first molding compound. Solder balls are formed on thesecond RDL structure. A semiconductor die is mounted on the first RDLstructure.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the embodiments, and are incorporated in and constitutea part of this specification. The drawings illustrate some of theembodiments and, together with the description, serve to explain theirprinciples. In the drawings:

FIG. 1 through FIG. 13 are schematic diagrams showing an exemplarymethod for fabricating a wafer level package (WLP) utilizing a moldedinterposer according to one embodiment of the invention;

FIG. 14 through FIG. 20 are schematic diagrams showing an exemplarymethod for fabricating a wafer level package (WLP) utilizing a moldedinterposer according to another embodiment of the invention; and

FIG. 21 shows metal vias comprising dummy metal vias, which have agreater via diameter than non-dummy metal vias.

DETAILED DESCRIPTION

In the following detailed description of the invention, reference ismade to the accompanying drawings, which form a part hereof, and inwhich is shown, by way of illustration, specific embodiments in whichthe invention may be practiced. These embodiments are described insufficient detail to enable those skilled in the art to practice theinvention. Other embodiments may be utilized and structural changes maybe made without departing from the scope of the present invention.

The following detailed description is, therefore, not to be taken in alimiting sense, and the scope of the present invention is defined onlyby the appended claims, along with the full scope of equivalents towhich such claims are entitled.

One or more implementations of the present invention will now bedescribed with reference to the accompanying drawings, wherein likereference numerals are used to refer to like elements throughout, andwherein the illustrated structures are not necessarily drawn to scale.The terms “die,” “semiconductor chip,” and “semiconductor die” are usedinterchangeably throughout the specification.

The terms “wafer” and “substrate” used herein include any structurehaving an exposed surface onto which a layer is deposited according tothe present invention, for example, to form the circuit structure suchas a redistribution layer (RDL). The term “substrate” is understood toinclude semiconductor wafers, but not limited thereto. The term“substrate” is also used to refer to semiconductor structures duringprocessing, and may include other layers that have been fabricatedthereupon.

FIG. 1 through FIG. 13 are schematic diagrams showing an exemplarymethod for fabricating a wafer level package (WLP) utilizing a moldedinterposer according to one embodiment of the invention.

As shown in FIG. 1, a carrier 300 is prepared. The carrier 300 may be areleasable substrate material. The carrier 300 may comprise glass,silicon, ceramic, metal, or any suitable supporting materials. At leasta dielectric layer or a passivation layer 310 is provided on a topsurface of the carrier 300. The passivation layer 310 may compriseorganic materials such as polyimide (PI) or inorganic materials such assilicon nitride, silicon oxide or the like.

As shown in FIG. 2, subsequently, a redistribution layer (RDL) structure410 is formed on the passivation layer 310. The RDL structure 410 actsas a front-side (or chip-side) RDL interposer that is able to fan outthe input/output (I/O) pads on a semiconductor die. The RDL structure410 may comprise at least one dielectric layer 412 and at least onemetal layer 414.

According to the embodiment, the dielectric layer 412 may compriseorganic materials such as polyimide (PI) or inorganic materials such assilicon nitride, silicon oxide or the like, but not limited thereto.

The metal layer 414 may comprise aluminum, copper, tungsten, titanium,titanium nitride, or the like. According to the illustrated embodiment,the metal layer 414 may comprise a plurality of fine-pitch traces,contact pads 418 exposed from a top surface of the dielectric layer 412,and contact pads 419 in direct contact with the passivation layer 310.

It is understood that the layers and layout of the metal layer 414 andthe contact pads 418, 419 are for illustration purposes only. Dependingupon design requirements, more layers of metal traces may be formed inthe RDL structure 410 in other embodiments.

As shown in FIG. 3, a template layer 500 is coated on the RDL structure410. For example, the template layer 500 may be a photoresist such asi-line photoresist, or a Directed Self Assembly (DSA) material, but isnot limited thereto.

As shown in FIG. 4, via openings 501 are formed in the template layer500. Each of the via openings 501 extends through the entire thicknessof the template layer 500. According to the embodiment, the via openings501 may expose the corresponding contact pads 418 for furtherconnection. According to the embodiment, the via openings 501 maycomprise at least one dummy via opening 501 a.

To form the via openings 501, the template layer 500 containing, forexample, a photoresist, may be subjected to a lithographic processincluding, but not limited to, a exposure process and a developmentprocess.

According to the embodiment, the via openings 501 may have the same viadiameter or dimension. According to other embodiments, the via openings501 may have different via diameters. For example, the dummy via opening501 a may have a greater via diameter than other non-dummy via openings501.

As shown in FIG. 5, after the formation of the via openings 501, metalvias 510 are formed within the via openings 501, respectively. Accordingto the embodiment, the via openings 501 are completely filled withmetal, such as copper, tungsten, aluminum, titanium, titanium nitride,or the like, to thereby form the metal vias 510. The metal vias 510 maybe formed by deposition, screen printing, or any suitable methods.

According to the embodiment, the metal vias 510 may comprise at leastone dummy metal via 510 a formed within the dummy via opening 501 a forthe purposes of stress relief or warpage control. The at least one dummymetal via 510 a may be disposed directly on a dummy pad 418 a. The dummypad 418 a is an electrically isolated pad. No signal passes through thedummy pad 418 a and the dummy metal via 510 a during operation of the ICpackage.

Optionally, a chemical-mechanical polishing (CMP) process may beperformed to remove excess metal outside the via openings 501. Accordingto the embodiment, the metal vias 510 may have a height that is equal tothe thickness t of the template layer 500.

According to the embodiment, the metal vias 510 may have the same viadiameter or dimension. According to other embodiments, the metal vias510 may have different via diameters. For example, the dummy metal via510 a may have a greater via diameter than other non-dummy metal vias510.

According to the embodiment, the metal vias 510 may function asinterconnects between the front-side RDL structure and the back-side RDLstructure, heat-dissipating features, or stress-adjusting features(dummy metal vias).

As shown in FIG. 6, after forming the metal vias 510, the template layer500 is completely removed, leaving the metal vias 510 including thedummy metal via 510 a intact. For example, the template layer 500, whencontaining photoresist, may be removed by plasma etching or ashingprocess. The contact pads 418 are exposed and the passive devicemounting areas 602, 603 are defined between the metal vias 510.

As shown in FIG. 7, a passive device 612 and a passive device 613 aremounted onto the exposed contact pads 418 within the passive devicemounting areas 602, 603, respectively. The passive device 612 may beelectrically connected to the contact pads 418 through the connectingelements 614, and the passive device 613 may be electrically connectedto the contact pads 418 through the connecting elements 615.

According to the embodiment, the connecting elements 614, 615 maycomprise solder bumps, copper bumps, micro-bumps, or copper pillars, butis not limited thereto. According to the embodiment, the passive devices612, 613 may comprise capacitors, resistors, or inductors, but is notlimited thereto. According to the embodiment, the passive devices 612,613 may be mounted onto the contact pads 418 by using surface mounttechnique (SMT).

As shown in FIG. 8, a molding compound 550 is applied. The moldingcompound 550 covers the metal vias 510, the passive devices 612, 613,and the RDL structure 410. The molding compound 550 may be subjected toa curing process. The molding compound 550 may comprise a mixture ofepoxy and silica fillers, but is not limited thereto. The layer ofmolding compound 550 is thicker than the thickness of the passivedevices 612, 613.

As shown in FIG. 9, a grinding process is performed. A top portion ofthe molding compound 550 is removed to expose top surfaces of the metalvias 510.

As shown in FIG. 10, a redistribution layer (RDL) structure 710 isformed on the molding compound 550 and on the metal vias 510. The RDLstructure 710 acts as a back-side (or PCB-side) RDL interposer. The RDLstructure 710 may comprise at least one dielectric layer 712 and atleast one metal layer 714.

According to the embodiment, the dielectric layer 712 may compriseorganic materials such as polyimide (PI) or inorganic materials such assilicon nitride, silicon oxide or the like, but not limited thereto.

The metal layer 714 may comprise aluminum, copper, tungsten, titanium,titanium nitride, or the like. According to the illustrated embodiment,the metal layer 714 may comprise a plurality of traces, and contact pads718 exposed from a top surface of the dielectric layer 712. Optionally,a dummy metal layer 714 a may be formed on the dummy metal via 510 a.The dummy metal layer 714 a is electrically isolated and is notconnected to other traces of the metal layer 714.

It is understood that the layers and layout of the metal layer 714 andthe contact pads 718 are for illustration purposes only. Depending upondesign requirements, more layers of metal traces may be formed in theRDL structure 710 in other embodiments.

Subsequently, solder balls 810 such as ball grid array (BGA) balls areformed on the contact pads 718. It is understood that a solder mask 802may be formed on the RDL structure 710. Prior to the formation of thesolder balls 810, an under-bump metallization (UBM) layer (notexplicitly shown) may be formed on the contact pads 718.

As shown in FIG. 11, after the formation of the solder balls 810, thepassivation layer 310 and the carrier 300 are removed to thereby exposethe contact pads 419 of the RDL structure 410. A wafer level moldedinterposer 100 is completed. Subsequently, a carrier 320 is bonded tothe wafer level molded interposer 100. The solder balls 810 are indirect contact with the carrier 320. An adhesive layer (not explicitlyshown) may be provided on the carrier 320. The carrier 320 may compriseglass, silicon, ceramic, metal, or any suitable supporting materials.

As shown in FIG. 12, a semiconductor die 11 and a semiconductor die 12are mounted on the RDL structure 410. The semiconductor die 11 andsemiconductor die 12 may be flip-chips. The semiconductor die 11 andsemiconductor die 12 are electrically connected to the RDL structure 410through the contact pads 419. The semiconductor die 11 and semiconductordie 12 are electrically connected to the RDL structure 710 through theRDL structure 410 and the metal vias 510.

Subsequently, a molding compound 560 may be formed to cover the RDLstructure 410 and the semiconductor dies 11, 12, thereby forming a waferlevel package 101. In order not to affect the property of the moldingcompound 550, the molding compound 560 may have a glass transitiontemperature that is lower than that of the molding compound 550.

According to the embodiment, the molding compound 560 may be cured at alower temperature, for example, a temperature lower than the glasstransition temperature of the molding compound 550. According to theembodiment, the molding compound 550 and the molding compound 560 mayhave different compositions. In other embodiments, the molding compound560 may be omitted.

As shown in FIG. 13, wafer level package 101 is singulated intoindividual die package 10 by dicing. It is understood that in otherembodiments each die package 10 may comprise only one die.

It is one technical feature of the invention that the passive devices612, 613 are embedded in the molded interposer 100 and encapsulated bythe molding compound 550. The overall size of the molded interposer ineach die package 10 can be reduced.

FIG. 14 through FIG. 20 are schematic diagrams showing an exemplarymethod for fabricating a wafer level package (WLP) utilizing a moldedinterposer according to another embodiment of the invention, whereinlike numeral numbers designate like layers, regions, or elements.

As shown in FIG. 14, likewise, a carrier 300 is prepared. Aredistribution layer (RDL) structure 410 is formed on the passivationlayer 310. The RDL structure 410 acts as a front-side (or chip-side) RDLinterposer that is able to fan out the input/output (I/O) pads on asemiconductor die. The RDL structure 410 may comprise at least onedielectric layer 412 and at least one metal layer 414.

A template layer 500 is coated on the RDL structure 410. For example,the template layer 500 may be a photoresist such as i-line photoresist,or a Directed Self Assembly (DSA) material, but is not limited thereto.Via openings 501 are formed in the template layer 500. Each of the viaopenings 501 extends through the entire thickness of the template layer500.

According to the embodiment, the via openings 501 may have the same viadiameter or dimension. According to other embodiments, the via openings501 may have different via diameters. According to other embodiments,some of the via openings 501 are dummy via openings.

As shown in FIG. 15, after the formation of the via openings 501, metalvias 510 are formed within the via openings 501, respectively. Accordingto the embodiment, the via openings 501 are completely filled withmetal, such as copper, tungsten, aluminum, titanium, titanium nitride,or the like, to thereby form the metal vias 510. The metal vias 510 maybe formed by deposition, screen printing, or any suitable methods.According to other embodiments, some of the metal vias 510 may be dummymetal vias.

Optionally, a chemical-mechanical polishing (CMP) process may beperformed to remove excess metal outside the via openings 501. Accordingto the embodiment, the metal vias 510 may have a height that is equal tothe thickness t of the template layer 500.

According to other embodiments, the metal vias 510 may have differentvia diameters. For example, as shown in FIG. 21, the metal vias 510 maycomprise dummy metal vias 510′, which have a greater via diameter thannon-dummy metal vias.

According to the embodiment, the metal vias 510 may function asinterconnects between the front-side RDL structure and the back-side RDLstructure, heat-dissipating features, or stress-adjusting features(dummy metal vias).

As shown in FIG. 16, after forming the metal vias 510, the templatelayer 500 is completely removed, leaving the metal vias 510 intact. Forexample, the template layer 500, when containing photoresist, may beremoved by plasma etching or ashing process.

As shown in FIG. 17, a molding compound 550 is applied. The moldingcompound 550 covers the metal vias 510 and the RDL structure 410. Themolding compound 550 may be subjected to a curing process. The moldingcompound 550 may comprise a mixture of epoxy and silica fillers, but isnot limited thereto. A grinding process is then performed. A top portionof the molding compound 550 is removed to expose top surfaces of themetal vias 510.

As shown in FIG. 18, a redistribution layer (RDL) structure 710 isformed on the molding compound 550 and on the metal vias 510. The RDLstructure 710 acts as a back-side (or PCB-side) RDL interposer. The RDLstructure 710 may comprise at least one dielectric layer 712 and atleast one metal layer 714.

According to the embodiment, the dielectric layer 712 may compriseorganic materials such as polyimide (PI) or inorganic materials such assilicon nitride, silicon oxide or the like, but not limited thereto.

The metal layer 714 may comprise aluminum, copper, tungsten, titanium,titanium nitride, or the like. According to the illustrated embodiment,the metal layer 714 may comprise a plurality of traces, contact pads 718exposed from a top surface of the dielectric layer 712.

It is understood that the layers and layout of the metal layer 714 andthe contact pads 718 are for illustration purposes only. Depending upondesign requirements, more layers of metal traces may be formed in theRDL structure 710 in other embodiments.

Subsequently, solder balls 810 such as ball grid array (BGA) balls areformed on the contact pads 718. It is understood that a solder mask 802may be formed on the RDL structure 710. Prior to the formation of thesolder balls 810, an under-bump metallization (UBM) layer (notexplicitly shown) may be formed on the contact pads 718.

As shown in FIG. 19, after the formation of the solder balls 810, thepassivation layer 310 and the carrier 300 are removed to thereby exposethe contact pads 419 of the RDL structure 410. A wafer level moldedinterposer 100 is completed. Subsequently, a carrier 320 is bonded tothe wafer level molded interposer 100. The solder balls 810 are indirect contact with the carrier 320. An adhesive layer (not explicitlyshown) may be provided on the carrier 320 to adhere the solder balls 810to the carrier 320. The carrier 320 may comprise glass, silicon,ceramic, metal, or any suitable supporting materials.

As shown in FIG. 20, a semiconductor die 11 and a semiconductor die 12are mounted on the RDL structure 410. The semiconductor die 11 andsemiconductor die 12 may be flip-chips. The semiconductor die 11 andsemiconductor die 12 are electrically connected to the RDL structure 410through the contact pads 419. The semiconductor die 11 and semiconductordie 12 are electrically connected to the RDL structure 710 through theRDL structure 410 and the metal vias 510.

Subsequently, a molding compound 560 may be formed to cover the RDLstructure 410 and the semiconductor dies 11, 12, thereby forming a waferlevel package. In order not to affect the property of the moldingcompound 550, the molding compound 560 may have a glass transitiontemperature that is lower than that of the molding compound 550.

According to the embodiment, the molding compound 560 may be cured at alower temperature, for example, a temperature lower than the glasstransition temperature of the molding compound 550. According to theembodiment, the molding compound 550 and the molding compound 560 mayhave different compositions. In other embodiments, the molding compound560 may be omitted. The wafer level package is singulated intoindividual die package 10 by dicing. It is understood that in otherembodiments each die package 10 may comprise only one die.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

1. A molded interposer, comprising: a layer of first molding compoundhaving a first side and a second side opposite to the first side; afirst redistribution layer (RDL) structure disposed on the first side; asecond redistribution layer (RDL) structure disposed on the second side;a plurality of metal vias embedded in the layer of first moldingcompound electrically connecting the first RDL structure with the secondRDL structure; and a passive device embedded in the layer of firstmolding compound, wherein the passive device is electrically connectedto the first RDL structure through a plurality of connecting elements.2. The molded interposer according to claim 1, wherein the plurality ofmetal vias comprises a dummy metal via.
 3. The molded interposeraccording to claim 1, wherein the plurality of connecting elements isembedded in the layer of first molding compound and is surrounded by thefirst molding compound.
 4. The molded interposer according to claim 1,wherein the first RDL structure comprises at least one first dielectriclayer and at least one first metal layer.
 5. The molded interposeraccording to claim 4, wherein the at least one first dielectric layercomprises an organic material or an inorganic material.
 6. The moldedinterposer according to claim 5, wherein the organic material comprisespolyimide.
 7. The molded interposer according to claim 5, wherein theinorganic material comprises silicon nitride or silicon oxide.
 8. Themolded interposer according to claim 4, wherein the at least one firstdielectric layer is in direct contact with the layer of first moldingcompound.
 9. The molded interposer according to claim 1, wherein thesecond RDL structure comprises a second dielectric layer and a secondmetal layer.
 10. The molded interposer according to claim 9, furthercomprising a solder mask on the second RDL structure.
 11. The moldedinterposer according to claim 9, further comprising a plurality ofsolder balls mounted on the second RDL structure.
 12. The moldedinterposer according to claim 1, wherein the layer of first moldingcompound has a thickness that is thicker than a thickness of the passivedevice.
 13. A semiconductor package, comprising: a molded interposeraccording to claim 1; and at least one semiconductor die mounted on thefirst RDL structure.
 14. The semiconductor package according to claim13, wherein the semiconductor die is encapsulated by a second moldingcompound.
 15. The semiconductor package according to claim 14, whereinthe first molding compound and the second molding compound havedifferent compositions.
 16. A method for fabricating a semiconductorpackage, comprising: providing a first carrier; forming a firstredistribution layer (RDL) structure on the first carrier; forming atemplate layer on the first RDL structure; forming via openings in thetemplate layer; forming metal vias in the via openings; removing thetemplate layer; mounting a passive device on the first RDL structure;molding the passive device and the metal vias with a layer of firstmolding compound; grinding the layer of first molding compound to exposeend surfaces of the metal vias; forming a second redistribution layer(RDL) structure on the layer of first molding compound; forming solderballs on the second RDL structure; and mounting a semiconductor die onthe first RDL structure.
 17. The method for fabricating a semiconductorpackage according to claim 16, further comprising: molding thesemiconductor die with a second molding compound.
 18. The method forfabricating a semiconductor package according to claim 17, furthercomprising: curing the second molding compound at a temperature that islower than a glass transition temperature of the first molding compound.19. The method for fabricating a semiconductor package according toclaim 17, wherein before mounting the semiconductor die on the first RDLstructure and after forming the solder balls on the second RDLstructure, the method further comprising: removing the first carrier,thereby forming a wafer level molded interposer; and bonding the waferlevel molded interposer to a second carrier, wherein the solder ballsare in direct contact with the second carrier.
 20. The method forfabricating a semiconductor package according to claim 16, wherein thetemplate layer is a photoresist layer.
 21. The method for fabricating asemiconductor package according to claim 16, wherein the passive devicecomprises a capacitor, a resistor, or an inductor.